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Shiau JC, Garcia-Diaz N, Kyle DE, Pathak AK. The influence of oviposition status on measures of transmission potential in malaria-infected mosquitoes depends on sugar availability. Parasit Vectors 2024; 17:236. [PMID: 38783366 PMCID: PMC11118549 DOI: 10.1186/s13071-024-06317-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Accepted: 05/03/2024] [Indexed: 05/25/2024] Open
Abstract
BACKGROUND Like other oviparous organisms, the gonotrophic cycle of mosquitoes is not complete until they have selected a suitable habitat to oviposit. In addition to the evolutionary constraints associated with selective oviposition behavior, the physiological demands relative to an organism's oviposition status also influence their nutrient requirement from the environment. Yet, studies that measure transmission potential (vectorial capacity or competence) of mosquito-borne parasites rarely consider whether the rates of parasite replication and development could be influenced by these constraints resulting from whether mosquitoes have completed their gonotrophic cycle. METHODS Anopheles stephensi mosquitoes were infected with Plasmodium berghei, the rodent analog of human malaria, and maintained on 1% or 10% dextrose and either provided oviposition sites ('oviposited' herein) to complete their gonotrophic cycle or forced to retain eggs ('non-oviposited'). Transmission potential in the four groups was measured up to 27 days post-infection as the rates of (i) sporozoite appearance in the salivary glands ('extrinsic incubation period' or EIP), (ii) vector survival and (iii) sporozoite densities. RESULTS In the two groups of oviposited mosquitoes, rates of sporozoite appearance and densities in the salivary glands were clearly dependent on sugar availability, with shorter EIP and higher sporozoite densities in mosquitoes fed 10% dextrose. In contrast, rates of appearance and densities in the salivary glands were independent of sugar concentrations in non-oviposited mosquitoes, although both measures were slightly lower than in oviposited mosquitoes fed 10% dextrose. Vector survival was higher in non-oviposited mosquitoes. CONCLUSIONS Costs to parasite fitness and vector survival were buffered against changes in nutritional availability from the environment in non-oviposited but not oviposited mosquitoes. Taken together, these results suggest vectorial capacity for malaria parasites may be dependent on nutrient availability and oviposition/gonotrophic status and, as such, argue for more careful consideration of this interaction when estimating transmission potential. More broadly, the complex patterns resulting from physiological (nutrition) and evolutionary (egg-retention) trade-offs described here, combined with the ubiquity of selective oviposition behavior, implies the fitness of vector-borne pathogens could be shaped by selection for these traits, with implications for disease transmission and management. For instance, while reducing availability of oviposition sites and environmental sources of nutrition are key components of integrated vector management strategies, their abundance and distribution are under strong selection pressure from the patterns associated with climate change.
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Affiliation(s)
- Justine C Shiau
- Department of Infectious Diseases, University of Georgia, Athens, GA, USA
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA
- Center for the Ecology of Infectious Diseases, Athens, GA, USA
| | - Nathan Garcia-Diaz
- The NSF-REU Program, Odum School of Ecology, Athens, GA, USA
- Department of Biology, Willamette University, Salem, OR, USA
- Department of Epidemiology, Brown University School of Public Health, Providence, RI, USA
| | - Dennis E Kyle
- Department of Infectious Diseases, University of Georgia, Athens, GA, USA
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA
- Department of Cellular Biology, University of Georgia, Athens, GA, USA
| | - Ashutosh K Pathak
- Department of Infectious Diseases, University of Georgia, Athens, GA, USA.
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA.
- Center for the Ecology of Infectious Diseases, Athens, GA, USA.
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Abbas H, Sajid MS, Rizwan HM, Tahir UB, Farooqi SH, Iqbal Z, Malik MA, Yaseen K, Maqbool M, Raza FA, Raza M, Fouad D, Ataya FS. Exploring mosquito abundance and Plasmodium infection through nested-PCR: implications for disease surveillance and control. Sci Rep 2024; 14:9871. [PMID: 38684775 PMCID: PMC11058852 DOI: 10.1038/s41598-024-60662-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 04/25/2024] [Indexed: 05/02/2024] Open
Abstract
The Plasmodium is responsible for malaria which poses a major health threat, globally. This study is based on the estimation of the relative abundance of mosquitoes, and finding out the correlations of meteorological parameters (temperature, humidity and rainfall) with the abundance of mosquitoes. In addition, this study also focused on the use of nested PCR (species-specific nucleotide sequences of 18S rRNA genes) to explore the Plasmodium spp. in female Anopheles. In the current study, the percentage relative abundance of Culex mosquitoes was 57.65% and Anopheles 42.34% among the study areas. In addition, the highest number of mosquitoes was found in March in district Mandi Bahauddin at 21 °C (Tmax = 27, Tmin = 15) average temperature, 69% average relative humidity and 131 mm rainfall, and these climatic factors were found to affect the abundance of the mosquitoes, directly or indirectly. Molecular analysis showed that overall, 41.3% of the female Anopheles pools were positive for genus Plasmodium. Among species, the prevalence of Plasmodium (P.) vivax (78.1%) was significantly higher than P. falciparum (21.9%). This study will be helpful in the estimation of future risk of mosquito-borne diseases along with population dynamic of mosquitoes to enhance the effectiveness of vector surveillance and control programs.
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Affiliation(s)
- Haider Abbas
- Department of Parasitology, Faculty of Veterinary Science, University of Agriculture, Faisalabad, 38040, Pakistan.
- Department of Pathobiology (Parasitology Section), KBCMA College of Veterinary and Animal Sciences, Narowal, Sub-Campus, University of Veterinary and Animal Sciences (UVAS), Lahore, Pakistan.
| | - Muhammad S Sajid
- Department of Parasitology, Faculty of Veterinary Science, University of Agriculture, Faisalabad, 38040, Pakistan
| | - Hafiz M Rizwan
- Department of Pathobiology (Parasitology Section), KBCMA College of Veterinary and Animal Sciences, Narowal, Sub-Campus, University of Veterinary and Animal Sciences (UVAS), Lahore, Pakistan
| | - Urfa B Tahir
- Department of Parasitology, Faculty of Veterinary Science, University of Agriculture, Faisalabad, 38040, Pakistan
- Department of Aquatic Animal Medicine, College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, China
| | - Shahid H Farooqi
- Department of Clinical Sciences (Medicine Section), KBCMA College of Veterinary and Animal Sciences, Narowal, Sub-Campus, University of Veterinary and Animal Sciences (UVAS), Lahore, Pakistan
| | - Zeeshan Iqbal
- Department of Animal Sciences (Livestock Section), KBCMA College of Veterinary and Animal Sciences, Narowal, Sub-Campus, University of Veterinary and Animal Sciences (UVAS), Lahore, Pakistan
| | - Muhammad A Malik
- Department of Parasitology, Faculty of Veterinary Science, University of Agriculture, Faisalabad, 38040, Pakistan
| | - Kashaf Yaseen
- Institute of Microbiology, University of Agriculture, Faisalabad, 38040, Pakistan
| | - Mahvish Maqbool
- Department of Parasitology, Faculty of Veterinary Science, University of Agriculture, Faisalabad, 38040, Pakistan
| | - Faiz A Raza
- Health Research Institute, National Institute of Health, Research Centre, , King Edward Medical University, Lahore, 54000, Pakistan
| | - Mohsin Raza
- Department of Basic Sciences (Physiology Section), KBCMA College of Veterinary and Animal Sciences, Narowal, Sub-Campus, University of Veterinary and Animal Sciences (UVAS), Lahore, Pakistan
| | - Dalia Fouad
- Department of Zoology, College of Science, King Saud University, PO Box 22452, Riyadh, 11495, Saudi Arabia
| | - Farid S Ataya
- Department of Biochemistry, College of Science, King Saud University, PO Box 2455, Riyadh, 11451, Saudi Arabia
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Pathak AK, Shiau JC, Freitas RC, Kyle DE. Blood meals from 'dead-end' vertebrate hosts enhance transmission potential of malaria-infected mosquitoes. One Health 2023; 17:100582. [PMID: 38024285 PMCID: PMC10665158 DOI: 10.1016/j.onehlt.2023.100582] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 06/08/2023] [Accepted: 06/08/2023] [Indexed: 12/01/2023] Open
Abstract
Ingestion of an additional blood meal(s) by a hematophagic insect can accelerate development of several vector-borne parasites and pathogens. Most studies, however, offer blood from the same vertebrate host species as the original challenge (for e.g., human for primary and additional blood meals). Here, we show a second blood meal from bovine and canine hosts can also enhance sporozoite migration in Anopheles stephensi mosquitoes infected with the human- and rodent-restricted Plasmodium falciparum and P. berghei, respectively. The extrinsic incubation period (time to sporozoite appearance in salivary glands) showed more consistent reductions with blood from human and bovine donors than canine blood, although the latter's effect may be confounded by the toxicity, albeit non-specific, associated with the anticoagulant used to collect whole blood from donors. The complex patterns of enhancement highlight the limitations of a laboratory system but are nonetheless reminiscent of parasite host-specificity and mosquito adaptations, and the genetic predisposition of An. stephensi for bovine blood. We suggest that in natural settings, a blood meal from any vertebrate host could accentuate the risk of human infections by P. falciparum: targeting vectors that also feed on animals, via endectocides for instance, may reduce the number of malaria-infected mosquitoes and thus directly lower residual transmission. Since endectocides also benefit animal health, our results underscore the utility of the One Health framework, which postulates that human health and well-being is interconnected with that of animals. We posit this framework will be further validated if our observations also apply to other vector-borne diseases which together are responsible for some of the highest rates of morbidity and mortality in socio-economically disadvantaged populations.
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Affiliation(s)
- Ashutosh K. Pathak
- Department of Infectious Diseases, University of Georgia, Athens, GA 30602, United States of America
- Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, GA 30602, United States of America
- Center for the Ecology of Infectious Diseases (CEID), University of Georgia, Athens, GA 30602, United States of America
- The SporoCore, CTEGD, University of Georgia, Athens, GA 30602, United States of America
| | - Justine C. Shiau
- Department of Infectious Diseases, University of Georgia, Athens, GA 30602, United States of America
- Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, GA 30602, United States of America
- Center for the Ecology of Infectious Diseases (CEID), University of Georgia, Athens, GA 30602, United States of America
- The SporoCore, CTEGD, University of Georgia, Athens, GA 30602, United States of America
| | - Rafael C.S. Freitas
- Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, GA 30602, United States of America
- The SporoCore, CTEGD, University of Georgia, Athens, GA 30602, United States of America
| | - Dennis E. Kyle
- Department of Infectious Diseases, University of Georgia, Athens, GA 30602, United States of America
- Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, GA 30602, United States of America
- The SporoCore, CTEGD, University of Georgia, Athens, GA 30602, United States of America
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, United States of America
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Omorou R, Bin Sa'id I, Delves M, Severini C, Kouakou YI, Bienvenu AL, Picot S. Protocols for Plasmodium gametocyte production in vitro: an integrative review and analysis. Parasit Vectors 2022; 15:451. [PMID: 36471426 PMCID: PMC9720971 DOI: 10.1186/s13071-022-05566-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 11/02/2022] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND The production of Plasmodium gametocytes in vitro is a real challenge. Many protocols have been described, but few have resulted in the production of viable and infectious gametocytes in sufficient quantities to conduct research on-but not limited to-transmission-blocking drug and vaccine development. The aim of this review was to identify and discuss gametocyte production protocols that have been developed over the last two decades. METHODS We analyzed the original gametocyte production protocols published from 2000 onwards based on a literature search and a thorough review. A systematic review was performed of relevant articles identified in the PubMed, Web of Sciences and ScienceDirect databases. RESULTS A total 23 studies on the production of Plasmodium gametocytes were identified, 19 involving in vitro Plasmodium falciparum, one involving Plasmodium knowlesi and three involving ex vivo Plasmodium vivax. Of the in vitro studies, 90% used environmental stressors to trigger gametocytogenesis. Mature gametocytemia of up to 4% was reported. CONCLUSIONS Several biological parameters contribute to an optimal production in vitro of viable and infectious mature gametocytes. The knowledge gained from this systematic review on the molecular mechanisms involved in gametocytogenesis enables reproducible gametocyte protocols with transgenic parasite lines to be set up. This review highlights the need for additional gametocyte production protocols for Plasmodium species other than P. falciparum.
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Affiliation(s)
- Roukayatou Omorou
- Malaria Research Unit, UMR 5246 CNRS-INSA-CPE-University Lyon1, University of Lyon, 69100, Villeurbanne, France.
| | - Ibrahim Bin Sa'id
- Malaria Research Unit, UMR 5246 CNRS-INSA-CPE-University Lyon1, University of Lyon, 69100, Villeurbanne, France.,Institut Agama Islam Negeri (IAIN) Kediri, 64127, Kota Kediri, Jawa Timur, Indonesia
| | - Michael Delves
- Department of Infection Biology, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1A 7HT, UK
| | - Carlo Severini
- Dipartimento Di Malattie Infettive, Istituto Superiore Di Sanità, Rome, Italy
| | - Yobouet Ines Kouakou
- Malaria Research Unit, UMR 5246 CNRS-INSA-CPE-University Lyon1, University of Lyon, 69100, Villeurbanne, France
| | - Anne-Lise Bienvenu
- Malaria Research Unit, UMR 5246 CNRS-INSA-CPE-University Lyon1, University of Lyon, 69100, Villeurbanne, France.,Service Pharmacie, Groupement Hospitalier Nord, Hospices Civils de Lyon, Lyon, France
| | - Stephane Picot
- Malaria Research Unit, UMR 5246 CNRS-INSA-CPE-University Lyon1, University of Lyon, 69100, Villeurbanne, France.,Institut de Parasitologie Et Mycologie Médicale, Groupement Hospitalier Nord, Hospices Civils de Lyon, Lyon, France
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Pathak AK, Shiau JC, Franke-Fayard B, Shollenberger LM, Harn DA, Kyle DE, Murdock CC. Streamlining sporozoite isolation from mosquitoes by leveraging the dynamics of migration to the salivary glands. Malar J 2022; 21:264. [PMID: 36100902 PMCID: PMC9472382 DOI: 10.1186/s12936-022-04270-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 08/12/2022] [Indexed: 12/05/2022] Open
Abstract
Background Sporozoites isolated from the salivary glands of Plasmodium-infected mosquitoes are a prerequisite for several basic and pre-clinical applications. Although salivary glands are pooled to maximize sporozoite recovery, insufficient yields pose logistical and analytical hurdles; thus, predicting yields prior to isolation would be valuable. Preceding oocyst densities in the midgut is an obvious candidate. However, it is unclear whether current understanding of its relationship with sporozoite densities can be used to maximize yields, or whether it can capture the potential density-dependence in rates of sporozoite invasion of the salivary glands. Methods This study presents a retrospective analysis of Anopheles stephensi mosquitoes infected with two strains of the rodent-specific Plasmodium berghei. Mean oocyst densities were estimated in the midguts earlier in the infection (11–15 days post-blood meal), with sporozoites pooled from the salivary glands later in the infection (17–29 days). Generalized linear mixed effects models were used to determine if (1) mean oocyst densities can predict sporozoite yields from pooled salivary glands, (2) whether these densities can capture differences in rates of sporozoite invasion of salivary glands, and (3), if the interaction between oocyst densities and time could be leveraged to boost overall yields. Results The non-linear effect of mean oocyst densities confirmed the role of density-dependent constraints in limiting yields beyond certain oocyst densities. Irrespective of oocyst densities however, the continued invasion of salivary glands by the sporozoites boosted recoveries over time (17–29 days post-blood meal) for either parasite strain. Conclusions Sporozoite invasion of the salivary glands over time can be leveraged to maximize yields for P. berghei. In general, however, invasion of the salivary glands over time is a critical fitness determinant for all Plasmodium species (extrinsic incubation period, EIP). Thus, delaying sporozoite collection could, in principle, substantially reduce dissection effort for any parasite within the genus, with the results also alluding to the potential for changes in sporozoites densities over time to modify infectivity for the next host. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-022-04270-y.
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Marques-da-Silva C, Peissig K, Walker MP, Shiau J, Bowers C, Kyle DE, Vijay R, Lindner SE, Kurup SP. Direct type I interferon signaling in hepatocytes controls malaria. Cell Rep 2022; 40:111098. [PMID: 35858541 PMCID: PMC9422951 DOI: 10.1016/j.celrep.2022.111098] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 04/13/2022] [Accepted: 06/23/2022] [Indexed: 11/17/2022] Open
Abstract
Malaria is a devastating disease impacting over half of the world’s population. Plasmodium parasites that cause malaria undergo obligatory development and replication in hepatocytes before infecting red blood cells and initiating clinical disease. While type I interferons (IFNs) are known to facilitate innate immune control to Plasmodium in the liver, how they do so has remained unresolved, precluding the manipulation of such responses to combat malaria. Utilizing transcriptomics, infection studies, and a transgenic Plasmodium strain that exports and traffics Cre recombinase, we show that direct type I IFN signaling in Plasmodium-infected hepatocytes is necessary to control malaria. We also show that the majority of infected hepatocytes naturally eliminate Plasmodium infection, revealing the potential existence of anti-malarial cell-autonomous immune responses in such hepatocytes. These discoveries challenge the existing paradigms in Plasmodium immunobiology and are expected to inspire anti-malarial drugs and vaccine strategies. Utilizing a transgenic Plasmodium strain expressing Cre recombinase that selectively ablates type I IFN receptor in only the infected hepatocytes, Marques-da-Silva et al. show that direct type I IFN signaling in the infected hepatocytes is both necessary and sufficient to control liver-stage malaria.
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Affiliation(s)
- Camila Marques-da-Silva
- Department of Cellular Biology, University of Georgia, Athens, GA, USA; Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA
| | - Kristen Peissig
- Department of Cellular Biology, University of Georgia, Athens, GA, USA; Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA
| | - Michael P Walker
- Department of Biochemistry and Molecular Biology, The Huck Center for Malaria Research, Pennsylvania State University, University Park, PA, USA
| | - Justine Shiau
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA; Department of Infectious Diseases, University of Georgia, Athens, GA, USA
| | - Carson Bowers
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA
| | - Dennis E Kyle
- Department of Cellular Biology, University of Georgia, Athens, GA, USA; Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA; Department of Infectious Diseases, University of Georgia, Athens, GA, USA
| | - Rahul Vijay
- Center for Cancer Cell Biology, Immunology and Infection, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
| | - Scott E Lindner
- Department of Biochemistry and Molecular Biology, The Huck Center for Malaria Research, Pennsylvania State University, University Park, PA, USA
| | - Samarchith P Kurup
- Department of Cellular Biology, University of Georgia, Athens, GA, USA; Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA.
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Nesbitt JE, Swei A, Hunt C, Dotson EM, Toner M, Sandlin RD. Cryoprotectant toxicity and hypothermic sensitivity among Anopheles larvae. Cryobiology 2020; 99:106-113. [PMID: 33382993 DOI: 10.1016/j.cryobiol.2020.12.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 11/30/2020] [Accepted: 12/23/2020] [Indexed: 01/06/2023]
Abstract
Laboratory rearing of mosquitoes is commonly practiced by researchers studying mosquito-borne infectious diseases and vector control methods. In the absence of cryopreservation methods to stabilize unique or genetically modified strains, mosquito lines must be continuously maintained, a laborious process that risks selection effects, contamination, and genetic drift. Towards the development of a cryopreservation protocol, several commonly used cryoprotectants were systematically characterized here both individually and as cocktails. Among first instar, feeding-stage An. gambiae and An. stephensi larvae, cryoprotectant toxicity followed the order of dimethyl sulfoxide > ethylene glycol > methanol. The resulting LD50 values were used as the basis for the development of cryoprotectant cocktail solutions, where formulation optimization was streamlined using Taguchi methods of experimental design. Sensitivity to hypothermia was further evaluated to determine the feasibility of cryoprotectant loading at reduced temperatures and slow cooling approaches to cryopreservation. The information described here contributes to the knowledge base necessary to inform the development of a cryopreservation protocol for Anopheles larvae.
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Affiliation(s)
- Jenny E Nesbitt
- BioMEMS Resource Center, Center for Engineering in Medicine, & Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
| | - Anisa Swei
- BioMEMS Resource Center, Center for Engineering in Medicine, & Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
| | - Catherine Hunt
- Centers for Disease Control and Prevention, Atlanta, GA, USA.
| | - Ellen M Dotson
- Centers for Disease Control and Prevention, Atlanta, GA, USA.
| | - Mehmet Toner
- BioMEMS Resource Center, Center for Engineering in Medicine, & Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
| | - Rebecca D Sandlin
- BioMEMS Resource Center, Center for Engineering in Medicine, & Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
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Pathak AK, Shiau JC, Thomas MB, Murdock CC. Field Relevant Variation in Ambient Temperature Modifies Density-Dependent Establishment of Plasmodium falciparum Gametocytes in Mosquitoes. Front Microbiol 2019; 10:2651. [PMID: 31803169 PMCID: PMC6873802 DOI: 10.3389/fmicb.2019.02651] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 10/30/2019] [Indexed: 12/29/2022] Open
Abstract
The relationship between Plasmodium falciparum gametocyte density and infections in mosquitoes is central to understanding the rates of transmission with important implications for control. Here, we determined whether field relevant variation in environmental temperature could also modulate this relationship. Anopheles stephensi were challenged with three densities of P. falciparum gametocytes spanning a ~10-fold gradient, and housed under diurnal/daily temperature range ("DTR") of 9°C (+5°C and -4°C) around means of 20, 24, and 28°C. Vector competence was quantified as the proportion of mosquitoes infected with oocysts in the midguts (oocyst rates) or infectious with sporozoites in the salivary glands (sporozoite rates) at peak periods of infection for each temperature to account for the differences in development rates. In addition, oocyst intensities were also recorded from infected midguts and the overall study replicated across three separate parasite cultures and mosquito cohorts. While vector competence was similar at 20 DTR 9°C and 24 DTR 9°C, oocyst and sporozoite rates were also comparable, with evidence, surprisingly, for higher vector competence in mosquitoes challenged with intermediate gametocyte densities. For the same gametocyte densities however, severe reductions in the sporozoite rates was accompanied by a significant decline in overall vector competence at 28 DTR 9°C, with gametocyte density per se showing a positive and linear effect at this temperature. Unlike vector competence, oocyst intensities decreased with increasing temperatures with a predominantly positive and linear association with gametocyte density, especially at 28 DTR 9°C. Oocyst intensities across individual infected midguts suggested temperature-specific differences in mosquito susceptibility/resistance: at 20 DTR 9°C and 24 DTR 9°C, dispersion (aggregation) increased in a density-dependent manner but not at 28 DTR 9°C where the distributions were consistently random. Limitations notwithstanding, our results suggest that variation in temperature could modify seasonal dynamics of infectious reservoirs with implications for the design and deployment of transmission-blocking vaccines/drugs.
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Affiliation(s)
- Ashutosh K. Pathak
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
- Center for Ecology of Infectious Diseases, University of Georgia, Athens, GA, United States
- Center for Tropical Emerging Global Diseases, University of Georgia, Athens, GA, United States
| | - Justine C. Shiau
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
| | - Matthew B. Thomas
- The Department of Entomology, Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA, United States
| | - Courtney C. Murdock
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
- Center for Ecology of Infectious Diseases, University of Georgia, Athens, GA, United States
- Center for Tropical Emerging Global Diseases, University of Georgia, Athens, GA, United States
- Odum School of Ecology, University of Georgia, Athens, GA, United States
- Center for Vaccines and Immunology, University of Georgia, Athens, GA, United States
- Riverbasin Center, University of Georgia, Athens, GA, United States
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